This invention relates generally to the enzymatic cleaning of hard surfaces and, more particularly to a liquid stabilized enzyme preparation and to its use for cleaning hard surfaces, above all in dairies/creameries.
Deposits containing proteins and fats are formed on surfaces of containers and pipes which come into contact with milk or milk products in the production and processing of milk. Such deposits, which are extremely difficult to remove, occur to a particularly marked extent in milking machines, milk collection trucks, tanks, pipelines and heaters. On account of the obstinate nature of the soils, equipment of the type in question is generally cleaned with strongly alkaline and, in some cases, also strongly acidic cleaners which have to handled with great care on account of their highly corrosive properties. In addition, where cleaners of this type are used on sensitive materials, they can be expected to cause corrosion unless special precautionary measures are taken. Before they discharged into the main drainage system, the cleaners have to be neutralized.
On account of the difficulties involved in using highly alkaline or strongly acidic cleaning solutions, there has been no shortage of attempts to develop cleaning solutions which clean as effectively as the strongly alkaline or highly acidic cleaners despite a substantially neutral pH value. Above all, it has been proposed to use enzymes, especially proteases, for this purpose. Numerous publications on this subject have appeared in the literature (cf. for example International patent application WO 96/6910 where more literature references can be found). Although in principle adequate cleaning is possible, even at a neutral pH, where proteases are used, the use of these enzymes is attended by other difficulties. Thus, liquid concentrates are preferably used for preparing the actual cleaning solution, especially in institutional cleaning. Unfortunately, liquid enzyme concentrates quickly lose their effectiveness in storage because the enzymes present are denatured or otherwise lose their activity. For this reason, numerous attempts have been made to improve the stability of liquid enzyme preparations in storage by the addition of so-called stabilizers. For example, the addition of boric acid or borates and soluble potassium salts and even the addition of polyhydric alcohols are widely practised. Unfortunately, these stabilizers still do not provide a totally satisfactory solution to the problem.
The problem addressed by the present invention also was to improve the stability of liquid enzyme preparations. Another problem addressed by the invention was to develop enzyme preparations which would be suitable for cleaning hard surfaces, especially in the dairy industry. In addition, these enzyme preparations would be suitable for the preparation of reusable cleaning solutions, above all of the type required for institutional cleaning.
It has surprisingly been found that the problems stated above can be solved by the addition of certain basic nitrogen compounds to the liquid enzyme preparations.